I'm with Shdw: supervise the first couple, then they can come into the school and rent solo to build their time whenever they want during regular biz hours (our dispatcher must be present). This is with the understanding that they don't let themselves get too far out of currency (about 3 weeks is my limit, on average. After that, we need to do some dual. But there's plenty of required dual instruction left in the course at this point anyway, so they're not wasting money.)
With navigation skills, I emphasize pilotage skills with all primary guys, whether they learn in the G1000 or steam gauges. I typically teach a lesson that incorporates landings at about 3-6 local airports. They must be able to fly me to each one using just a chart. Essentially, this is what happens at the END of a cross country flight (the set up to entering the traffic pattern, communication with tower, etc.), so I find that immersion in this skill makes the first dual cross country flight a piece of cake. Then that allows me to emphasize (on the first dual cross country) sticking to the planned route, updating actual times on the navlog, using those pilotage skills to verify position along the planned route, and to introduce communication with approach/departure controllers.
In the subsequent dual cross country lessons (or even on the way back on the first one--if they're sharp!), I'll talk about using the VORs, GPS, diverting in the case of abnormalities/emergencies, and other communication items like Flight Following, opening/closing VFR flight plans, etc. in preparation for the next couple dual cross countries.
And, yes, I still teach calculations using the E6B wiz-wheel. Several of the CFIs I know don't even teach that anymore and go straight to the glass ops. I find this creates glassy-eyed pilots with hollow heads who cannot navigate their way out of a paper bag when the MFD is turned off. Of course, I eventually turn them to plan flights using a flight computer, AOPA planner, or something more efficient, but my idea is to make sure they understand the fundamentals of planning and navigation before they try to create shortcuts.
-A.S.